Femoroacetabular impingement (FAI) is a reduction in hip joint clearance that causes hip pain and may predispose the hip joint to osteoarthritis (OA). Altered biomechanics are considered the key initiator of OA. Patients with FAI often present with chondrolabral damage and restrictions in range of motion, suggesting that FAI alters cartilage/labrum contact mechanics and hip kinematics. Recent studies suggest that FAI may also cause primary or adaptive changes to muscle activation and force. Previous clinical and basic biomechanics studies have failed to elucidate the link between FAI, altered biomechanics and OA due to oversimplified approaches or inaccurate testing equipment. Our long term goal is to improve the diagnosis and treatment of FAI by quantifying hip biomechanics. To support this goal, we propose a R21-level research study to demonstrate the feasibility of using a combined experimental and computational protocol to quantify joint kinematics, muscle forces/activations, and cartilage/labrum contact mechanics in the human hip. We will use a combination of dual fluoroscopy and camera-based marker tracking to quantify lower limb kinematics during activities of daily living. Musculoskeletal (MS) models will estimate muscle forces/activations and finite element (FE) models will predict chondrolabral mechanics. In the past, our MS models assumed a static hip joint center and pre-defined muscle attachments and our FE models assumed boundary and loading conditions from the literature. In this R21, we will compare MS model (Aim 1) and FE model (Aim 2) predictions between models that are subject-specific with those that assume pre-defined or literature-based inputs. After determining the required level of model complexity and after conducting power analyses with the pilot data from this R21, we will pursue R01 level funding extending our computational and experimental protocols to further investigate the biomechanics of FAI.